Guidance system, method and devices thereof

ABSTRACT

A guidance system, a method and a device for dynamically guiding a surgical needle catheter onto an organ to be surgically operated of a patient. In particular, the disclosure relates to a guidance system, a method and a device to aid in the percutaneous kidney puncture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Patent ApplicationNo. PCT/IB32019/053083, filed 15 Apr. 2019, which claims priority toPortuguese Patent Application No. 110686, filed 13 Apr. 2018, each ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

One exemplary aspect of the present disclosure relates to a guidancesystem, a method and a device for dynamically guiding a surgical needlecatheter or other medical device or instrument onto an organ or otherbody part of a patient for a surgical operation. In particular, oneaspect of the disclosure relates to a guidance system, method and deviceto aid percutaneous kidney puncture.

BACKGROUND References

Document US2014/0051985 A1 discloses a target finding system identifiesa surgical target such as a kidney stone by disposing an emitter such asa magnetic source behind or adjacent the surgical target and employing acircuit to identify an axis to the emitter, thus Defining an axis orpath to the surgical target. Document WO 03/103492 A1 relates to adevice for localizing an instrument or device, comprising at least onerotatable magnet producing a magnetic moment perpendicular to the axisof the device independently from said instrument or device.

Document WO 2017/120434 A1 relates to devices for guiding an instrumentinto a body of a patient, at a targeted point of entry and along aninsertion path at a targeted insertion angle, are described herein, suchas a guide for an access needle in a PCNL procedure for accessing thekidney to remove kidney stones, the devices comprising a base component,a guide assembly, and optionally an insertion mechanism. Document EP2967411 A1 relates a surgical locator circuit identifies a surgicaltarget such as a kidney stone by disposing an emitter such as a magneticsource behind or adjacent the surgical target and employing the circuitto identify an axis to the emitter, thus defining an axis or path to thesurgical target.

These facts are disclosed in order to illustrate the technical problemaddressed by the present disclosure. All references are herewithincorporated by reference herein in their entirety.

Additional References

-   [1] Z. Yaniv, E. Wilson, D. Lindisch, and K. Cleary,    “Electromagnetic tracking in the clinical environment,” Medical    Physics, vol. 36, pp. 876-892, March 2009.-   [2] N. D. Inc. Available:    http://www.ndigital.com/medical/products/aurora/-   [3] B. C. Meyer, O. Peter, M. Nagel, M. Hoheisel, B. B.    Frericks, K. J. Wolf, et al., “Electromagnetic field-based    navigation for percutaneous punctures on C-arm CT: experimental    evaluation and clinical application,” European Radiology, vol. 18,    pp. 2855-2864, December 2008.-   [4] J. Huber, I. Wegner, H. P. Meinzer, P. Hallscheidt, B.    Hadaschik, S. Pahernik, et al., “Navigated renal access using    electromagnetic tracking: an initial experience,” Surgical Endoscopy    and Other Interventional Techniques, vol. 25, pp. 1307-1312, April    2011.-   [5] J. Krücker, A. Viswanathan, J. Borgert, N. Glossop, Y. Yang,    and B. J. Wood, “An electro-magnetically tracked laparoscopic    ultrasound for multi-modality minimally invasive surgery,” in    International Congress Series, 2005, pp. 746-751.-   [6] M. A. Nixon, B. C. McCallum, W. R. Fright, and N. B. Price, “The    effects of metals and interfering fields on electromagnetic    trackers,” Presence: Teleoperators and Virtual Environments, vol. 7,    pp. 204-218, 1998.-   [7] G. S. Fischer and R. H. Taylor, “Electromagnetic tracker    measurement error simulation and tool design,” in Medical Image    Computing and Computer-Assisted Intervention—MICCAI 2005, ed:    Springer, 2005, pp. 73-80.-   [8] A. Bosnjak, G. Montilla, R. Villegas, and I. Jara, “An    Electromagnetic Tracking System for Surgical Navigation with    registration of fiducial markers using the iterative closest point    algorithm,” in Information Technology and Applications in    Biomedicine (ITAB), 2010 10th IEEE International Conference on,    2010, pp. 1-5.-   [9] F. Banovac, E. Wilson, H. Zhang, and K. Cleary, “Needle biopsy    of anatomically unfavorable liver lesions with an electromagnetic    navigation assist device in a computed tomography environment,”    Journal of vascular and interventional radiology, vol. 17, pp.    1671-1675, 2006.-   [10] E. B. Levy, H. Zhang, D. Lindisch, B. J. Wood, and K. Cleary,    “Electromagnetic tracking-guided percutaneous intrahepatic    portosystemic shunt creation in a swine model,” Journal of Vascular    and Interventional Radiology, vol. 18, pp. 303-307, February 2007.-   [11] M. Nagel, M. Hoheisel, U. Bill, K. Klingenbeck-Regn, W. A.    Kalender, and R. Petzold, “Electromagnetic tracking system for    minimal invasive interventions using a C-arm system with CT option:    First clinical results—art. no. 69180G,” Medical Imaging 2008:    Visualization, Image-Guided Procedures, and Modeling, Pts 1 and 2,    vol. 6918, pp. G9180-G9180 423, 2008.-   [12] C. M. Wegner and D. B. Karron, “Surgical navigation system and    method using audio feedback,” ed: Google Patents, 2000.-   [13] W. G. Gardner, 3-D audio using loudspeakers: Springer Science &    Business Media, 1998.-   [14] M. K. Dobrzynski, S. Mejri, S. Wischmann, and D. Floreano,    “Quantifying information transfer through a head-attached    vibrotactile display: principles for design and control,” Biomedical    Engineering, IEEE Transactions on, vol. 59, pp. 2011-2018, 2012.

GENERAL DESCRIPTION

One aspect of the present disclosure relates to a guidance system fordynamically guiding a medical device or instrument such as a surgicalneedle catheter onto an organ to be surgically operated of a patient,comprising:

-   -   an EM, electromagnetic, catheter for inserting into the patient        for defining the desired location to be reached by the needle        catheter;    -   an EM, electromagnetic, tracker of the surgical catheter        location and orientation;    -   a display of a 2D concentric ring target;    -   wherein said target being on a plane intersecting the tip of the        EM catheter and perpendicular with the surgical catheter        orientation;    -   continuously displaying a projection of a line concurrent with        the needle catheter onto said target plane;    -   continuously displaying a plurality of concentric rings centred        around the tip of the EM catheter.

One aspect of the present disclosure also relates to a guidance system,method and device to aid the percutaneous kidney puncture.

In an embodiment, the guidance system may further comprise an inner ringcorresponding to a predetermined surgically acceptable region for thecatheter.

In an embodiment, the guidance system may further comprise anintermediate ring corresponding to a predetermined surgicallyinacceptable region for the catheter.

Another aspect of the present disclosure relates to a method forimplementing the guidance system of the present application.

Another aspect of the present disclosure relates to a medical devicecomprising the guidance system of the present application.

Another aspect of the present disclosure relates to a method and deviceto aid the percutaneous kidney puncture.

One aspect of the present disclosure also relates to a guidance systemfor dynamically guiding a surgical needle catheter or other medicaldevice or instrument onto an organ of a patient, which is to besurgically operated, comprising:

-   -   an EM, electromagnetic, catheter, arranged for inserting into        the patient and for defining a desired location to be reached by        the surgical needle catheter;    -   an EM, electromagnetic, tracker arranged for tracking of a        location and orientation of the surgical needle catheter; and    -   an electronic data processor arranged for:        -   displaying a 2D concentric-ring target;        -   continuously displaying a projection of a line concurrent or            coincident with the surgical needle catheter onto said            target, wherein said target is on a plane intersecting a tip            of the EM catheter and being perpendicular to the            orientation of the surgical needle catheter;        -   continuously displaying a plurality of concentric rings            centred around the tip of the EM catheter.

In an embodiment, said concentric rings comprise an inner ringcorresponding to a predetermined surgically acceptable region for thesurgical needle catheter.

In an embodiment, said inner ring is centered around the tip of the EMcatheter and has a radius of less than or equal to 1 mm, of less than orequal to 2 mm, of less than or equal to 3 mm, of less than or equal to 5mm, of less than or equal to 8 mm, or of less than or equal to 10 mm.

In an embodiment, said concentric rings comprise an intermediate ringcorresponding to a predetermined surgically inacceptable region for thesurgical needle catheter.

In an embodiment, said intermediate ring is centered around the tip ofthe EM catheter and has a radius of less than or equal to 25 mm, of lessthan or equal to 30 mm, of less than or equal to 35 mm, of less than orequal to 40 mm, of less than or equal to 45 mm, or of less than or equalto 50 mm.

In an embodiment, said concentric rings comprise a further ring having avariable diameter depending on a spatial difference between surgicalneedle catheter tip and the target.

In an embodiment, said further ring has a visual characteristic which ischanged when the surgical needle catheter tip deviates from the target,in particular the visual characteristic being changed when the surgicalneedle catheter tip goes beyond the target.

In an embodiment, said visual characteristic is a colour of the furtherring, a thickness of the further ring, a fill-in of the further ring, orcombinations thereof.

An embodiment comprises a 3D sound interface arranged for providingspatialized sounds according to a spatial difference between surgicalneedle catheter tip and the target.

An embodiment comprises a vibration interface arranged for providingspatialized vibration feedback using vibration motors, according to thespatial difference between surgical needle catheter tip and target.

In an embodiment, the plurality of concentric rings are displayed aroundthe target on the plane intersecting a tip of the EM catheter and beingperpendicular to the orientation of the surgical needle catheter.

An embodiment comprises the surgical needle catheter arranged forsurgical operation of the organ.

In an embodiment, said organ is the kidney and the dynamically guidingof the surgical needle catheter is for percutaneous renal access.

It is also described a medical device comprising the guidance system ofany of the disclosed embodiments.

It is also disclosed a method for implementing a guidance system fordynamically guiding a surgical needle catheter onto an organ of apatient, which is to be surgically operated,

-   -   said system comprising an EM, electromagnetic, catheter,        arranged for inserting into the patient for defining a desired        location to be reached by the surgical needle catheter; an EM,        electromagnetic, tracker arranged for tracking of a location and        orientation of the surgical needle catheter; and an electronic        data processor;    -   said method comprising carrying out by said data processor the        steps of:        -   displaying a 2D concentric-ring target;        -   continuously displaying a projection of a line concurrent or            coincident with the surgical needle catheter onto said            target, wherein said target is on a plane intersecting the            tip of the EM catheter and perpendicular with the surgical            needle catheter orientation;        -   continuously displaying a plurality of concentric rings            centred around the tip of the EM catheter.

It is also disclosed non-transitory storage media including programinstructions for implementing a guidance system for dynamically guidinga surgical needle catheter onto an organ to be surgically operated of apatient, the program instructions including instructions executable by adata processor to carry out any of the disclosed methods.

One of the main functions of the surgical needle catheter is to beinserted into the body, in particular a body cavity, for surgicalpurposes. Additionally, a surgical needle can be used to create apercutaneous path towards the target anatomical structure to bemanipulated during surgery. Alternatively, another device having atracker EM sensor and having the function of being inserted into thebody for surgical purposes can also be used.

The guidance system, method and device of the present disclosure is ableto easily and safely guide the percutaneous renal access (PRA),guaranteeing that anatomical structure, in particular an organ, is notaccidentally perforated and responding to current surgeon's demands. Thesystem, method and device also improves and/or optimizes the punctureplanning increasing the certainty of reaching a specific target insidethe kidney.

One of the exemplary aspects of the present disclosure is to provide anew system and method to aid percutaneous kidney puncture. The guidancesystem of one aspect the present disclosure is able to easily and safelyguide PRA (percutaneous renal access), guaranteeing that any organ isnot accidentally perforated and responding to current surgeon's demands.The disclosure is also able to optimize the puncture planning increasingthe certainty of reaching a specific target inside the kidney.

The easily and safely guiding the of percutaneous renal access can befurther specified in a set of specific phases:

-   -   Phase 1: Motion tracking of the surgical tools—real-time motion        tracking sensors (electromagnetic motion tracking (EMT)        technology to monitor the position and orientation of the needle        and catheter during PRA. This phase creates a virtual        environment where the information retrieved by motion tracking        sensors is used to guide the surgeon during whole puncture        stage.    -   Phase 2: User guide interface—discloses different ways to        provide user feedback about the spatial relationship between the        surgical tools. The outcome is a simple and intuitive user        interface, at least capable of guiding the surgeon throughout        the entire renal access stage, namely puncture planning and        needle insertion.

Since the need of PRA has increased in recent years, the improvement inpatient care and simplification of this surgical step, through theproposed phases, may lead to several exemplary non-limiting advantages:

-   -   Broaden the PRA procedure to surgeons less specialized and        familiarized with MISs (Minimal Invasive Surgeries) due to an        intuitive and efficient platform. Today, due to its high        learning curve, only 10% of specialized urologist perform this        procedure;    -   Eliminate X-ray imaging during PRA, which significantly        decreases patient radiation exposure, especially for the surgeon        who performs this intervention more than once a day;    -   Improve preoperative planning through the availability of        accurate and complete tracking of the surgical tools;    -   Reduce surgery time, because one of the most time-consuming        steps may be shortened through an easier puncture;    -   Minimize potential surgical complications caused by human        errors, image misinterpretation and hand/eye coordination        limitations;    -   Decrease errors related to target movements and tissue        deformations, by permanently monitoring them during PRA;    -   Reduce surgery costs.

An overview of the particular ways in which the state of the artregarding PRA is improved by the present disclosure, can be madeaccording to the following points:

-   -   A critical review that addresses the methodologies and        techniques for conducting kidney targeting and the puncture step        during PCNL (percutaneous nephrolithotomy);    -   A new real-time navigation system, based in EMT, to plan and        guide PRA. It shows virtual surgical tools (needle and catheter)        in 3D or 2D, according to the 3D spatial information provided by        EMT sensors coupled in their tips. This framework aids the        surgeon to navigate a tracked needle towards a catheter placed        near the anatomical target;    -   3D sound interface capable of providing spatialized sounds from        different point sources surrounding the user. These sounds are        defined and positioned in a 3D space according to the current        orientation error, that is calculated as the spatial difference        between the needle tip and the puncture trajectory that the        surgeon must follow; and/or    -   Vibration device capable of providing spatialized vibration        feedback using different vibration motors. These motors        positioned and coupled to an elastic headband according to the        eight cardinal points. Each motor generates a vibration pattern        that depends on the spatial difference between the needle tip        and the puncture trajectory that the surgeon must preferably        follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures provide exemplary embodiments for illustrating thedisclosure and should not be seen as limiting the scope of invention.

FIG. 1: Schematic representation of the surgical setup according to anembodiment when using the Aurora system [2]. The Aurora field generatorcreates an electromagnetic working space where the needle and cathetercan be manipulated. Both tools are wired connected through the SystemControl Unit, SCU, to the herein described KidneyNav software accordingto the disclosure.

FIG. 2: Overview of the animal trial for percutaneous collecting systemaccess.

FIG. 3: Representation of the new surgical setup considering themulti-sensorial interface: 1) NeedleView, 2) 7.1 headphones and 3)vibrotactile headband.

FIG. 4: Representation of the NeedleView interface (right). The verticalarrows (white, green, yellow and red) show the size correspondencebetween the circles diameter and the kidney anatomy.

FIG. 5: Representation of the ray-plane projection method to create theNeedleView visual interface.

FIG. 6: Representation of 3D sound configurations around the listenervia a direct path. Each sound source is represented by a red circle. a)8 sources equally spaced by α=45 degrees; b) 16 sources equally spacedby α=22.5 degrees; c) 12 sources with two different angles: α=22.5 andβ=56.25 degrees.

FIG. 7: Representation of the visual guidance interface while playing asound source.

FIG. 8: Step function that gives the sound loudness gain according tothe error region.

FIG. 9: Boxplots showing the percentage of times that the useraccurately mark the audio or vibration source. Average values are shownby the cross symbol.

FIG. 10: Boxplots showing the angulation error when marking the audio orvibration source. Average values are shown by the cross symbol.

FIG. 11: Time needed for planning and puncturing for whole elements ofthe naive and expert group: 3D=3D View; 2D=NeedleView; A=Audio;V=Vibration; 3D/2D=3D view+NeedleView; 3D/2D/A=3D view+NeedleView+Audio;3D/2D/V=3D view+NeedleView+Vibration.

FIG. 12: Comparison between guidance strategies. The arrow points to thebest method when comparing the average times for planning andpuncturing. The asterisk gives the statistical significances (two-wayANOVA): without asterisk p>0.05; *p≤0.05; **p≤0.01; ***p≤0.001;****p≤0.0001.

FIG. 13: Boxplots of the errors from the preferred trajectory, accordingto the profiles shown in FIG. 18: 3D=3D View; 2D=NeedleView; A=Audio;V=Vibration; 3D/2D/A=3D view+NeedleView+Audio; 3D/2D/V=3Dview+NeedleView+Vibration.

FIG. 14: Error profile deviations from the preferred trajectory whenplanning or puncturing according to different guidance strategies. Thevertical line indicate the end of the planning procedure.

FIG. 15: Representation of the visual guidance interface while theneedle approaches (or even goes beyond) the intended target fordistances of: 70 mm to the target, 30 mm to the target, 3 mm to thetarget and 15 mm beyond the target; using a ring concentric with thetarget, whose diameter varies directly (e.g. proportionally) with thedistance to the target and which changes (e.g. in color, fill-in,thickness) if the distance is negative (i.e. beyond the target).

FIG. 16: Photographic illustration of the needle trying to puncture.

FIG. 17: Boxplots of the average times for planning and puncturing inthe animal trial.

FIG. 18: Target depiction with 4 concentric rings and projection of aline coincident with the surgical needle catheter onto said targetwhich, for illustration purposes, has not been represented perpendicularto the orientation of the surgical needle catheter.

DETAILED DESCRIPTION

One exemplary aspect of the present disclosure relates to a guidancesystem, a method and a device for dynamically guiding a surgical needlecatheter or other medical instrument onto an organ of a patient. Inparticular, the present disclosure relates to a guidance system, methodand device to aid in the percutaneous kidney puncture.

The following pertains to motion tracking for surgical navigation, inparticular electromagnetic tracking for puncture guidance, further inparticular the Aurora system (NDI, Waterloo, Canada). EMT potentiallycan be used to guide PRA interventional procedures, since it can provideaccurate tracking without the line-of sight requirements. In order totrack medical devices such as needles and catheters this systemcomprises the following hardware devices: field generator, sensorinterface units (SIU), system control unit (SCU) and electromagneticsensors. The Aurora™ system is but one example of an EMT system, usedaccording to the present disclosure. Although it is to be appreciatedsimilar systems will work equally well with the disclosed technology.

In accordance with one exemplary embodiment, the SCU includes one ormore processors, a graphics processing unit (GPU), memory, an audiointerface for the headphones discussed hereinafter, an audio card orequivalent audio processing system and a controller for actuating anytactile feedback.

The SCU can interface with the SIUs using any known communicationprotocol and/or interface(s) including wired or wireless interfaces. TheSCU and KidneyNAV can also be connected to one or more display unitesand configured to display the visual guidance as discussed herein.Communication between the SCU, KidneyNAV and the surgeon's feedbackmechanisms can be wired or wireless, such as using Bluetooth®, to sendsignals to the headphones and/or tactile feedback device(s) such as thevibrotactile headband. It is to further be appreciated that the SCU andKidneyNAV could be combined with virtual reality or augmented realitygoggles such that the information displayed on the display could bepresented in these goggles in 2D or 3D.

The planar field generator emits a low-intensity and varyingelectromagnetic field that establishes a working volume. When theelectromagnetic sensors are placed inside this working volume, smallcurrents are induced in the sensors. These induced voltages are measuredby the SCU that calculates the sensors position and orientation. The SCUalso transmits the positional data to a host computer using a serialport connector or other communication port/protocol, for subsequentprocessing and navigation.

The electromagnetic sensors are connected via a SIU to the SCU. This SIUworks as an analog-to-digital converter and amplifier of the electricalsignals from the sensors to an SCU, decreasing the possibility ofelectromagnetic interferences in the operating room.

The low electromagnetic field strength can safely pass through humantissue, making it an ideal system to track surgical instruments insertedinside the human body through natural orifices or small incisions.

Finally, the electromagnetic sensors can be embedded into the workingsurgical tools or devices. For this embodiment, one may preferablyacquire two modified surgical instruments: one 18 G/180 mm Chiba needle;and one ureteral catheter with 1.1 mm diameter and 2 m length. Bothincorporate an electromagnetic sensor with 5 DOF at its tip, not beingable to infer the orientation about their long axis (roll axis).

The following pertains to methods. In particular, the following pertainsto EMT Navigation. The introduction of EMT navigation, for example theAurora system, in the PRA workflow will modify the first two PCNLsurgical stages: (a) the trans-urethral catheter placement and (b) thepercutaneous puncture.

The following pertains to trans-urethral catheter placement. On thefirst surgical step, an Uretero-Reno-Fiberscope Flex-X™ from Karl Storzor comparable device is trans-urethrally placed from the urethra towardsthe desired renal calyx.

In contrast to the currently used technology, the catheter is guidedtowards the anatomic target using the Flex-X™ camera without requiringother medical imaging modalities. Furthermore, since Flex-X has aworking channel of 1.2 mm, it allows the integration of a positioningand orientation electromagnetic sensor with six DOFs (Degrees ofFreedom) at its tip from Aurora motion tracking system (NDI, Waterloo,Canada). Here the electromagnetic sensor, located at the Flex-X™ tip,acts as an anatomic target locator, operating as a GPS (global positionsystem) for the puncture site.

According to Flex-X™ tip orientation it is possible to place the sensorin the desired calyx, where the calculi target is located, allowing thesurgeon to choose the best virtual trajectory for the percutaneouspuncture.

The following pertains to puncture stage. On the second surgical step, avirtual trajectory will be determined by the relative orientation andposition differences retrieved in real-time by both needle and catheterEMT sensors.

This virtual trajectory display will be used to confirm that thecatheter and needle are parallel aligned. If necessary, the surgeon canredefine the catheter orientation, and the virtual trajectory will bereal-time updated. This procedure provides constant real-timepositioning feedback (beep sound and/or 3D representation) to thesurgeon, allowing the surgeon to accomplish a perfect orientation of theneedle at all times, even in the presence of anatomical changes, such astract dilatation, respiratory movements and needle deflections, amongothers.

The beep sound was generated by asynchronously and repetitively playinga MP3 or comparable sound file with 0.15 seconds of duration. This soundwas played with a frequency calculated with the common linear equation:y=mx+b. The slope m of such equation was given by the distance betweenthe catheter and needle EMT sensors. The embodiment includes that thefrequency should increase when the needle tip is close to the cathetertip. The x and b were experimentally calculated (x=17 and b=60), bymoving one sensor towards and away from another and by qualitativelyevaluate the sound feedback, although other values are possible.

Concerning this new tracking disclosure, FIG. 1 shows a new surgicalsetup. Now it is possible to track accurately the needle tip with anelectromagnetic sensor (5) and the anatomical target using a trackedcatheter (6). In contrast with the Polaris system, the Aurora toolshould be wired connected to the SCU (4 and 7) that communicates withthe KidneyNav software (1 and 2).

The following pertains to Animal Preparation. This EMT approach wastested using different female pigs (Sus scrofus domesticus) with variousweights (25-35 Kg). Before surgery, the animals were fed with liquidsfor 3 days and then restrained from food (24 hours) and water (6 hours)before the surgical tests.

All procedures were carried out with the pigs under general anesthesia,with 5.0 mm endotracheal intubation and mechanical ventilation.Pre-anesthesia medication consisted of an intramuscular injection of 32mg/mL azaperone, reconstituted with 1 mg/mL midazolam with a dose rangeof 0.15-0.20 mL/kg.

The venous access was obtained through an intravenous line placed at themarginal ear vein. The anesthesia was induced with 3 μg/kg fentanyl, 10mg/kg thiopental sodium, and 1 mg/kg vecuronium. It was maintained with1.5% to 2.0% of sevoflurane and a perfusion of 1 mg/kg per hour ofvecuronium. All pigs received an intramuscular injection of 1 gceftriaxone before the tests beginning.

The following pertains to Experiments. In vitro and in vivo experimentswere performed to evaluate the accuracy and performance of the EMTframework for PRA. Ex vivo tests aimed to understand and quantify theAurora system technical characteristics, such as precision, accuracy andcritical system problems e.g., electromagnetic interferences. On theother hand, in vivo animal trials, with more dynamic characteristics,aimed to define and evaluate the surgical setup, planning and puncturetime, system reliability and efficiency for PRA.

The following pertains to laboratory trials, in particularelectromagnetic interferences. The purpose of a test was to investigateerror sources that might compromise the EMT accuracy during surgicalnavigation.

This test starts by putting the field generator on a position arm whichoffers flexible setup options around an object of interest, e.g.abdominal phantom placed in an electromagnetic free environment. Then,both the needle and catheter sensors, adjacently fixed to each other,were moved randomly along the working volume. The positional differencebetween both sensors was transmitted and stored to a host computer. Inabsence of electromagnetic interference, the difference between bothsensors should be a constant with negligible variances.

Because one aims to quantify the mean accuracy within this navigationvolume, different surgical tools made with different material wereplaced inside the navigation volume and in the vicinity of theelectromagnetic sensors. For each material, one compared the sensorspositional difference with the values acquired when any electromagneticinterference exists. The following materials were evaluated due to theirusage during PCNL:

-   -   Stainless steel: the majority of medical instruments are        manufactured with stainless steel due to its strength and        durability. One evaluates electromagnetic interferences of this        material by using different surgical instruments such as        ureterorenoscope, cytoscope, telescopes, scalpel and forceps.    -   Tungsten Carbide: is used in the manufacture of such instruments        as needle holders, scissors, pin cutters and pliers;    -   Mild steel: this metal is almost obsolete because its tendency        to chip and contaminate other instruments. Only scissors were        used to test this material.    -   Aluminium: only certain instrument parts and cases are        manufactured from aluminum due to its lightweight, e.g. handle        and or body of the instrument and not the tool itself (scissors        and forceps)    -   Titanium: The high cost of using titanium for instrument        manufacture is often prohibitive. Due to its lightweight, it is        commonly used for microsurgery tools, e.g. forceps, laparoscopic        tools.

The following pertains to Animal Trials. The animal experimental studieswere approved by the ethical review boards of Minho University, Braga(Portugal). The animal was monitored by a veterinary anesthesiologiststhroughout the study.

This experiment starts by placing the pig in supine position. This firststage is used to identify the ureteral orifices of both kidneys using arigid cystoscope. Then, ureterorenoscopies were performed bilaterally.An ureterorenoscope with 1.2 mm working channel allowed to put theureteral catheter into the desired puncture site. FIG. 2 represents theexperiment setup.

After positioning the ureterorenoscope at the puncture site, resortingto a direct video view, the surgeon inserted the needle into thecalyceal fornix by the following actions:

-   -   1. Orientate the needle through a virtual direct path, aligning        the needle tip with the target position;    -   2. Puncture the first skin layer and repeat step 1);    -   3. Drive the needle through the selected path, until it reaches        the anatomic target (confirmed by the ureterorenoscope video        camera).

The percutaneous punctures were performed for each pig at the ureterhalf-way between the kidney and the urinary bladder and in renal calycesin order to evaluate the puncture location influence.

The following pertains to Outcome Measurements. The following surgicalparameters were evaluated in order to ascertain if the proposed trackingsolution confers any advantage to the surgeon performing PCNL:

-   -   a. Planning time: time needed by the surgeon to evaluate the        virtual trajectory displayed at the software and orient the        needle at skin surface;    -   b. Number of attempts: number of tries to reach the puncture        site;    -   c. Puncture time: time needed to perform a successful renal        puncture from the skin surface to the puncture target. When the        needle tip was visible by the ureteroscope camera, the needle        pass was considered complete.

The experiments were performed by an expert surgeon and a resident inorder to avoid a supposed bias related to surgeon ability. Furthermore,the puncture location was also analyzed as a variable influencing theabove outcomes.

The following pertains to Results, in particular of Laboratory Trials,in particular of Electromagnetic Interferences. The needle and catheterwere adjacently placed with 10 millimeters distance between them. Norelevant interferences were found when using stainless steel, titaniumor tungsten carbide. In these cases, the maximum error was notsignificant (<0.2 mm). The catheter can be placed inside theureterenoscope or cytoscope working channel without losing trackingaccuracy.

When using mild steel or aluminum instruments one found that the errorincrease proportionally with the distance between the sensors and theferromagnetic material. Maximum errors of 8 and 15 mm were found whenmaneuvering EMT sensors in the working volume periphery and a mild metalor aluminum, respectively, were placed in the middle of the workingvolume. When aluminum tools, e.g. forceps or scissors were manipulated˜7 cm away from the electromagnetic sensors, the maximum error was lessthan 1 mm.

The following pertains to Animal Trial. Overall 24 punctures weresuccessfully performed without any complications: 12 in middle ureterand 12 in the kidney calyx (lower, middle or upper kidney calix).

Table 1 summarizes measured outcomes for whole procedures. Planning timewas longer for the ureter case than the kidney (median 15 versus 13seconds, range 14-18 versus 11-16; p=0.1).

Likewise, time to achieve ureteral puncture was significantly longerthan kidney puncture, requiring 51 (range 45-67) and 19 (range 14-45)seconds (p<0.01), respectively. Two attempts were needed to carry outthe ureteral puncture, contrasting with a single attempt for the kidney(p<0.05). When comparing the puncture time, planning time, number ofattempts and final distance (Table 2), regarding the percutaneous renalaccess for the upper, middle and lower calyx, one achievednon-significant differences (p>0.05).

TABLE 1 Surgical outcomes according to puncture location. MeasuresPuncture Site Median Kidney (min − max) calyx Ureter P* Planning Time(s) 13 15 0.1 (11 − 16) (14 − 18) Puncture Time (s) 19 51 0.003 (14 −48) (45 − 67) Number of Attempts  1  2 0.01 (1 − 2) (2 − 4) FinalDistance  2.1  1.9 0.79 (1.5 − 2.7) (1.4 − 2.7) *Mann-Whitney testbetween kidney calyx and ureter

TABLE 2 Surgical outcomes according to the kidney calyx. Measures KidneyCalyx Median (min − max) Upper Middle Lower P* Planning Time (s) 15 1413 0.51 (12 − 17) (12 − 16) (10 − 15) Puncture Time (s) 25 19 20 0.9 (14− 48) (14 − 48) (14 − 40) Number of Attempts  1  1  1 0.62 (1 − 2) (1 −2) (1 − 2) Final Distance  2.0  2.1  2.1 0.79 (1.8 − 2.2) (1.5 − 2.5)(1.9 − 2.7) *Mann-Whitney test

When results from experts and residents are analyzed independently(Table 3), one verifies that, despite non-significant statisticaldifferences (p>0.05), there was a slight tendency of higher puncture andplanning times, as well as, a great number of attempts for residents.

TABLE 3 Surgical outcomes according to the kidney calyx and ureterpunctures. Kidney Calyx Ureter Measures Median (min − max) ResidentExpert p* Resident Expert P* Planning Time (s) 15 13 0.06 17 15 0.08 (13− 17) (10 − 16) (17 − 19) (15 − 16) Puncture Time (s) 29 19 0.38 66 480.06 (14 − 48) (14 − 34) (64 − 68) (46 − 50) Number of Attempts  1  10.98  4  2 0.99 (1 − 2) (1 − 2) (3 − 4) (2 − 3) Final Distance  2.1  2.00.72  1.8  1.6 0.12 (1.5 − 2.2) (1.8 − 2.7) (1.6 − 1.9) (1.4 − 2.0)*Mann-Whitney Test

Computer navigation systems, based in EMT technologies, are anattractive research area and have been suggested for different surgicalprocedures [9]. From the PRA point of view, it was performed several invitro, ex vivo and in vivo experiments to evaluate the efficiency of theKidneyNav framework, working together with EMT Aurora system.

The following pertains to the Aurora System. The great advantage ofAurora over optical systems, such Polaris, was the ability to tracksmall EMT sensors inside the human body without any line-of-sightrequirements [1].

The disclosure preferably demands endoscopic imaging for real-timemonitoring of the puncture target and two EMT sensors. The ureteralcatheter and needle, both integrating an Aurora EMT sensor at its tip,are able to retrieve in real-time the position and orientation. Thecatheter remained associated to the puncture target (worked as a 3Dreal-time locator) and was permanently monitored by the EMT sensor andthe ureterorenoscope video camera. Therefore, it followed in real-timeall the anatomic tissues deformations and movements—originated by therespiratory cycle and also by those induced to the patient. The surgeoninserted the needle guided by the virtual puncture path displayed in theKidneyNav interface.

An important proof-of-concept step was also achieved by succeeding inperforming a direct ureteral puncture, even though the procedure tooksignificantly more time, due to the ureteral movements, ureter smalldiameter and soft consistence, which made the needle glide on itssurface. Even though these preliminary results provide prospective pathsfor other applications (e.g. Percutaneous Ureteral Lithotripsy), themain objective was to further corroborate the efficiency of the purposedpuncture method in a small target cavity.

Interesting of note, no difference in operator skill was found inperforming the puncture. Whereby, it is reasonable to speculate thatthis tracking solution may reduce the number of cases needed to performan appropriate collecting system access and make it easier. Specificliterature reports that the learning curve completion for PCNL surgicalcompetence around 60 cases. Considering the kidney access one of themost challenges phases, in this study a resident achieved the same skilllevel of an expert surgeon with only twelve cases.

The safety efficacy of different surgical positions for accessing thecollecting system has been a controversial issue, with currently noestablished best practice consensus. The use of a real-time 3Dtrajectory proposed in this work may broaden the use of supine positionfor the whole PCNL procedure. In this case, the surgeon does not need toreposition the patient (decreasing surgery time in about 30-40 minutes)and may improve levels of comfort for both patient and surgeon asdescribed in the literature. On the other hand, when the patient isrepositioned, there is a reduced risk of access dislodging, since thecatheter remains permanently monitored by the EMT sensor and theureterorenoscope camera.

Medical imaging assistance to puncture commonly requires approximately10 minutes, often guided by X-Ray based imaging and in vitro conditions.Comparing the related results, one has achieved a puncture timeimprovements between 75 and 85% without any X-Ray need.

Due to its advantages, the Aurora system has been extensively tested inrecent years in different clinical and nonclinical environments [1].Different works have reported errors of 0.71±0.43, with a maximum 3Droot mean square positional accuracy of 2.96 mm. Although these valuesare higher than the Polaris accuracy, it remains highly suitable for PRApurposes [11].

Although Yaniv et al. [1] reported that electromagnetic systems may besusceptible to environment interference in the operating room, thetechniques disclosed herein did not experience any kind of interferencethat could tamper the tracking information. By evaluating the impact ofthe surgical instruments, composed by different metals (aluminum,stainless steel, titanium, tungsten carbide and mild steel), one createsa more comprehensive list of requirements when using an EMT system inthe operating room. Results show that only mild steel or aluminum caninfluence the error-proneness of EMT sensors. However, this may notrepresent a problem since mild steel or aluminum instruments have beenreplaced by stainless steel ones [1]. But, in order to guarantee thatthe system accuracy is not degraded, aluminum or mild metal shouldpossibly not be used during the surgical procedure. At least, theyshould not be placed inside the working volume while the puncture isbeing performed.

Other important evaluation data was the intrusiveness of such modality.In contrast to other navigation frameworks, it will not increase theprocedural time because the proposed system does not have a large setupand does not require additional steps like immobilization of thepatient, preparation of the hardware, registration setup, orinitializing of navigation components [1].

The motion tracking field generator should be placed on the surgicalstretcher as near as possible to the kidney abdominal area (or otherarea being operated upon) and with an appropriately orientation tominimize the probability of interference distortions. All other possibleelectromagnetic disturbance sources, such as, cellphones and usualoperating room equipment should kept at least 1.5 meters away from theworking volume. The KidneyNav interface will advise when some possibleinterference exists or if the instruments are being maneuvered at thelimits of the working volume.

When compared to the Polaris, the Aurora system can use wires totransmit the information between the EMT sensors and control unit and afield generator positioned close to the interventional area. However,these did not restrict the access to the abdominal area, not being alimiting factor in any of the experiments. Since sensors are placedinside the human body during all operation, there was no need for aregistration and calibration procedure.

Hereupon, the proposed solution may be the simple and easy way to selectand follow the correct puncture path, as well as acquire the requiredskill to perform PCNL regardless of calculus site, large or multiplerenal calculi, or an ectopic or malformed kidney.

The following pertains to multi-sensorial guidance interface. Visualinterfaces have been proposed over the years for biomedical applicationscovering the diagnostic, planning and guidance of several surgicalprocedures. Currently available visual interfaces, aid surgeonsthroughout the entire surgical procedure, reducing the risks andpossible unknowns [12].

Although new algorithms and registration techniques have been exploredto link virtual and real worlds, the interpretation of 2D images or 3Dreconstructions are still a challenging task. For intraoperative complexprocedures, visual interfaces may only provide good guidancecapabilities for specific points of view. Often, surgeon's skills andexpertise strongly affect the surgical outcome.

In addition to the information received through our sight, audio andtactile information are nowadays becoming commonplace ways oftransmitting information. Hearing and touch are the second and thirdmajor human senses, respectively, being two promising and uniquealternatives or complementary modalities for visual systems.Consequently, it allows the development of innovative hand- andeyes-free interfaces.

The aspect of using new ways of feedback for puncture guidance duringPRA, concerns the ability to create accurate and precise localization ofthe needle tip with respect to the anatomical target.

The following pertains to audio feedback systems. First audio feedbackmethodologies have been explored due to their ability to create, processand localize sounds from complex data in a 3D space. Since computationalrequirements to generate audio are much smaller than for 3D graphics,these auditory interfaces were created in order to overcometechnological limitations, such as limited real-time refresh rates,image poor resolution and rendering capabilities.

Nowadays, audio feedback is an attractive area of exploration for a widerange of medical or nonmedical applications [13]. Due to the ability ofsurrounding the listener with sounds at specific locations, soundapplications have emerged to create an immersive environments forcomputer games [13], warning systems for civil aircraft [13], flight andmilitary simulations, guidance interfaces to blind people, night visionsystems, airplane cockpit, guidance to athletes, augmented realitysystems, perceptual representation of biomedical data and heart ratemonitors [12].

To the best of our knowledge, audio feedback for computer aided surgeryhave only been only explored by four groups [12]. Preliminary works werereported by Weber et al. [12], describing an audio system to guide abiopsy needle when perforating a gelatin phantom. Although they describean application with great potential, quantitative or qualitative resultsare not reported.

Another audio feedback system, presented by Cho et al., guides thesurgeon to a cochleostomy location. The authors generate warning toneswhen an optical tracked drill is closer to the target (tones of 300 Hz)or reaching the target (tones of 900 Hz).

From the analyzed literature, audio feedback advantages include fasterprocessing data, high temporal resolution, parallel data streams andimproves the degree of focus on the task at hand. Moreover, it createsan effective way to overcome the visual overload from complex data anddue to its omnidirectionality, i.e., allows perceptions from any pointin space without occlusions.

Low spatial resolution and perception, sound interferences, dependenceof user are the main shortcomings [12] of the above techniques.

The following pertains to vibration feedback systems. Similar to audiofeedback systems, the usage of vibrotactile feedback has also beendescribed in literature. For instance, vibrotactile has been reported asuseful in improving awareness of critical events such driver responses,spatial guidance in pedestrian navigation, alert systems for blind orvisually impaired persons, gesture guidance, human-computer interactionimproving realism with tactile display interfaces, immersive sensationsin computer games, body posture improvements (Janssen et al., 2010), andassistance in rehabilitation.

Hence, various innovative and disruptive devices were proposed for beingattached for different human parts, e.g., head [14], fingers, forearm,hand, upper body, tongue and foot.

The head has been the most preferable site for vibration wearables(e.g., headbands [14], headphones and glasses). They have been studiedin various environments, because they do not restrict the usersmaneuverability (e.g., devices used in fingers, forearm, and hand),verbal communication (e.g., devices used in the tongue) or touchsensation (e.g. gloves).

Even being an preferred place for receiving feedback, some authorswarned that the head sensitivity is not the same throughout whole area.Myles et al. and Weber et al. study and evaluate the sensibility of headsurface. Both studies stated that vibration sensitivity is different fordifferent head locations, where the crown of the scalp was reported asthe least sensitive to vibration stimuli relative to areas close to thetemples, forehead, and back of the head (most sensitive area).

Even ergonomics, positional efficiency and accuracy of a vibrotactileheadband has already been studied [14], pattern codification forguidance, the preferred number of actuators and testing in realsituations are still needed.

The following pertains to audio and vibration feedback for PRA. From thereported applications, it is clearly seen that audio or vibrotactilefeedback can considerably highlight 3D orientation and guidance,decreasing the dependence of visual faculties and improving insight intovirtual data. They often improve perception capabilities, which may bealtered due to continued procedures, fatigue, inaccurate insight anddecrease of attention.

When compared to other medical technologies routinely used for guidance(e.g. motion tracking systems, robotic devices, improved surgical tools,imaging systems), audio or vibrotactile feedback are relativelyunexplored. The wider acceptance of such modalities will mostly dependon the quality and quantity of transmitted information, but also if theuser can effectively learn how to use it.

In addition to the 3D feedback provided from the KidneyNav interface,this work explores the potentiality of new guidance interfaces includingan improved 2D visual interface (from now on referred as NeedleView), avibrotactile headband and 7.1 headphones able of generating 3Ddirectional sounds.

The following pertains to methods, in particular to an overview. In thissection, we propose the application of a multisensorial feedbackplatform combined with the previous described 3D view of the KidneyNavto develop a more intuitive guidance system. Upon each occurrence of theneedle tip deviating from the path to reach the target, a set of audioand/or vibration signals will be generated and transmitted to thesurgeon.

Such information will be perceived from a vibrotactile headband, 7.1headphones and the NeedleView, that will aware and guide the surgeontowards a preferred path (FIG. 3).

The following pertains to NeedleView. Sight devices used to supportinstruments aligning (e.g. weapons, airplanes, telescopes, etc.) wereprior art to the disclosure of the NeedleView. FIG. 4 shows thedeveloped target sight. Vertical and horizontal alignment for theperfect needle orientation is achieved when a blue sphere is placedinside a white disk (although other color schemes are possible).

Once the needle is aligned in the right position, a green label showingthe distance to the target will be displayed to the user. If anydeviation occurs, a red label will be shown. Likewise any sight, theneedle tip will reach accurately the anatomical target if the needle isinserted along the path without any deviation. Different color disks(white, green, yellow and red in FIG. 4) may be used to implement ascore system that gives information about the current error with respectto the target:

-   -   White region informs the user that the needle will reach the        target within a 2 mm error (approximately the size of a minor        kidney calyx);    -   Green region informs the user that the needle will reach the        target with a maximum error of 10 mm (proximately the side of a        kidney medulla);    -   Yellow region informs the user that the needle will reach the        target with a maximum error of 25 mm (proximately the side of a        kidney pelvis);    -   Yellow region informs the user that the needle will reach the        target with a maximum error of 50 mm (proximately the side of a        kidney size);

The blue sphere is drawn according to a method that projects a ray in a3D plane (FIG. 5). Let p_(N)(x, y, z) be the current needle position and{right arrow over (v)}_(N)(x, y, z) a 3D vector defined at p_(N)(x, y,z) and the orientation of the needle tip. Let P be a plane defined bythe target position p_(T)(x, y, z) and a normal {right arrow over(v)}_(T)(x, y, z). The needle will accurately reach the target (p_(T)(x,y, z)) if a ray {right arrow over (R_(N))} starting at its tip positionat p_(N) (x, y, z) follows a direction {right arrow over (v)}_(N)(x, y,z).

The NeedleView represents graphically the intersection of the ray {rightarrow over (R_(N))} with P at a projection point p′_(N)(x, y, z). Whenp_(T)(x, y, z)=p′_(N)(x, y, z) the user is following the correcttrajectory.

Any point p_(Ray)(x, y, z) along {right arrow over (R_(N))} can becalculated according to (Equation 1):

p _(Ray)(x,y,z)=p _(N)(x,y,z)+t×{right arrow over (v)}_(N)(x,y,z)  Equation 1

where t is a free constant that gives different points away fromp_(N)(x, y, z). p′_(N)(x, y, z) is calculated by solving this tparameter (Equation 2).

$\begin{matrix}{t = {{- \frac{{{\overset{\rightarrow}{p}}_{N}\left( {x,y,z} \right)} \cdot {{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}}{{{\overset{\rightarrow}{v}}_{N}\left( {x,y,z} \right)} \cdot {{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}}} = {- \frac{{{{\overset{\rightarrow}{p}}_{N}\left( {x,y,z} \right)}} \times {{{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}} \times {\cos (\theta)}}{{{{\overset{\rightarrow}{v}}_{N}\left( {x,y,z} \right)}} \times {{{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}} \times {\cos (\alpha)}}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

{right arrow over (p)}_(N)(x, y, z) is a vector defined between p_(N)(x,y, z) and p_(T)(x, y, z); θ is the angle between {right arrow over(p)}_(N)(x, y, z) and {right arrow over (v)}_(T)(x, y, z); and α is theangle between {right arrow over (v)}_(N)(x, y, z) and {right arrow over(v)}_(T)(x, y, z). Finally, by solving Equation 2 in Equation 1,p′_(N)(x, y, z) is given by Equation 3:

$\begin{matrix}{{p_{N}^{\prime}\left( {x,y,z} \right)} = {{p_{N}\left( {x,y,z} \right)} + {\left( {- \frac{{{{\overset{\rightarrow}{p}}_{N}\left( {x,y,z} \right)}} \times {{{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}} \times {\cos (\theta)}}{{{{\overset{\rightarrow}{v}}_{N}\left( {x,y,z} \right)}} \times {{{\overset{\rightarrow}{v}}_{T}\left( {x,y,z} \right)}} \times {\cos (\alpha)}}} \right) \times {{\overset{\rightarrow}{v}}_{N}\left( {x,y,z} \right)}}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Note that if dot({right arrow over (v)}_(N)(x, y, z), {right arrow over(v)}_(T)(x, y, z))=0, the needle orientation and target plane areperpendicular. To avoid such cases, at the beginning of the puncture andafter performing an initial orientation, {right arrow over (v)}_(T)(x,y, z) is automatically set as {right arrow over (v)}_(N)(x, y, z).

The following pertains to audio feedback. 3D audio feedback was obtainedby creating positional sounds varying one or more of the followingcharacteristics: pitch (sound frequency), loudness (sound intensity) andplaying location (sound source with a particular 3D location).

The following pertains to audio channels. According to the number ofsource sounds it is possible to classify sound systems as mono (1discrete audio channel), stereo (2 discrete audio channels) and surround(N audio channels).

A mono system only produce sounds from a single source, being not ableto transmit surround information. Stereo systems are able to reproducesound from two independent sound sources, placed at the left and rightof the listener. By changing the gain of each channel, it is possible tonotice sound in the line between the left and right channel. Commonmethods to produce 3D sounds based on stereo systems are based onmodifications of audio amplitude or on the delaying the arrival of thesound into the listener. Lastly, true surround sound is created byplacing sound sources anywhere in 3D space. The spatial sound resolutionis dependent in the number of sound sources surrounding the listener.

This work makes use of 7.1 headphones for producing surrounding audio: 7directional channels left, center, right, left surround, right surround,left rear surround and right rear surround and 1 subwoofer that enhanceslow frequencies. These headphones are able to produce spatialized soundin the horizontal listener plane. Still, the reproduction of elevationsounds is still limited.

The following pertains to Audio APIs. A 3D audio space can be createdusing an audio API. The most known are OpenAL and EAX (EnvironmentalAudio Extensions) from Creative Technology, Ltd. and DirectSound3Dproduced by Microsoft. EAX works as an audio extension for OpenAL andDirectSound3D and implements different audio effects (e.g. echo,reverberation, distortion, occlusions, exclusions, obstructions).Therefore, it cannot be used, by itself, to create a 3D sound world. Onthe other hand, DirectSound3D and OpenAL includes common functionalities[13]:

-   -   Audio Contexts: an audio environment can be described as        consisting of a listener and source sounds. One single context        is created for each sound card;    -   Spatialized Audio: a listener is created per context and is        positioned in a 3D world. Then, different audio sources are also        defined and placed in the same world. The spatialization is        accomplished by attaching a specific buffer to each audio        source. A buffer consists in the audio data originated from        loading a sound file (e.g. MPR, PCW) or by creating configurable        sound functions such as sinusoids with different frequencies.    -   High level functions to play, restart, rewind or loop each audio        source under the sound card or CPU;    -   Audio Attenuation functions: the audio is attenuated as function        (linear or exponential) of the distance between the listener and        audio source;    -   Static and Streaming Audio: can play data completely stored in        memory and stream buffers while continually read new portion of        data at specific time intervals; Pitch and frequency        manipulation;    -   Doppler effect: automatically modifies the audio source        frequencies giving an effect of different moving velocities of        an audio source.    -   DirectSound3D presents some additional capabilities over OpenAL,        since it supports audio effects and live voice. However, it is        limited to wave files data, is more difficult to implement and        only works under Windows®. In contrast, OpenAL supports the most        used operating systems such Windows®, Android®, Linux® and        Apple®. Consequently, OpenAL was chosen as the most suitable API        platform concerning the trade-off between potentialities and        facility of implementation. By combining all the above        characteristics in a single framework, it is possible to create        a fully immersive sound environment, with audio sources placed        at strategic positions, to precisely and accurately aid the        needle tip orientation with respect to the target position.

The following pertains to 3D audio world. The audio feedback preferablyfollows the same strategy as the NeedleView. The aspect of using audioto correct needle orientation is based on creating and positioningdifferent audio sources in a 3D space around a centered listener (FIG.6).

Sound from different positions will reach the listener with differentdirections. By internally analyzing this direction, the listener will beable to ascertain the corrections to be made. The error at thehorizontal plane P of the NeedleView are used to activate or deactivatethe playing sources.

Since the reliability of audio spatialization is dependent on the numberof sources, three different configurations were tested (FIG. 6): 8, 16and 12 source configurations (8SC, 16SC, and 12SC in FIG. 6-a, -b and-c, respectively).

The following pertains to positional feedback. Errors from the preferredtrajectory are used to set different audio buffers and toactivate/deactivate audio sources from where the sound will be emanated.

Since changes in the needle orientation are correlated with changes inthe listened sound, three different strategies were implemented toaccurately alert and guide the listener during needle insertion. All ofsound strategies are based on the variation of the sound pitch, loudnessand source location.

The following pertains to a first sound strategy—SS1. The audio loudnessis calculated according an error function, with respect to the preferredtrajectory. When the needle is following the correct path, i.e., thetarget can be reached with an accuracy less T_(err) mm, no sound will beproduced (loudness is 0). As shown in FIG. 7, for errors higher thanT_(err), i.e. the needle starts moving away from the correct path, thesound source with opposite direction to the error will start playing.

D_(err) is calculated through the Euclidean distance from the verticaland horizontal errors and is used to control the source loudness gainfrom 0 (no sound is listened) to 1 (maximum sound output). The loudnesswas controlled using a step function (FIG. 8) that highlights when theerror increases from a specific error region (white, green, green andred) to another.

Each sound source played a sinusoid signal with frequency Sf, phase Sp,duration Sd and a sleep interval between each tone Ssleep.

Ssleep was proportionally to the distance to reach the target. BeingmaxSleep and minSleep the maximum and minimum allowable sleep intervals,respectively, and max_(dist) and min_(dist) the maximum and minimumaffecting distances, respectively, Ssleep was calculated according toEquation 4.

$\begin{matrix}{{{Ssleep} = {{m*{dist}\; 2{target}} + {{mi}\; n\; {Sleep}}}}{{{Where}\mspace{14mu} m} = {\frac{{maxSleep} - {\min \; {Sleep}}}{{max\_ dist} - {min\_ dist}}.}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

The following pertains to a second sound strategy—SS2. Same strategy asSS1, but now instead of not playing any sound when the needle isfollowing the correct path (with an accuracy less T_(err) mm), a soundwith distinct frequency S₂f is playing by all sound sources.

The following pertains to a third sound strategy—SS3. From literature,it is known that horizontal and vertical sounds are well discriminated,but it is more difficult to differentiate between front and back sounds.Efficiencies of about 50% are commonly reported [13].

Due to this shortcomings, this third strategy tries to improvefront-back resolution by adding distinguish frequency tones, where frontor back sources are playing. Two frequencies were used: frequenciesSf_(front) for sources placed from 0° to 180° degrees; and Sf_(back) forsources placed from 181° to 359° degrees. The frequency gap is used torapidly ascertain if the needle tip should be moved to the front or backfor orientation correction. With such differences, one expects toincrease the localization performance, relative to the first strategy(SS1 and SS2).

The following pertains to a fourth sound strategy—SS4. In order toimprove and enhance the spatial sound resolution, SS3 was furthermodified by introducing an intermittent sound at the four cardinalsources. These sound sources will be playing in an alternate mode twosinusoid waves: one with the parameters discussed at SS1 (S f, Sp,Ssleep and Sd) and another with distinct frequency S₄f and duration S₄d.

For all strategies, when the needle tip reaches the target, a messagesound is generated (e.g. “Target Achieved”). Here, the surgeon mustanalyze the ureterenoscope video to inspect if the needle is near thetarget.

The following pertains to 3D vibrotactile feedback. In addition to theNeedleView and 3D sound, this work also explored vibrotactile sensationfor needle guidance. Due to the desirable site of the head for providingfeedback [14], one can chose to manufacture a headband with multipleactuators that vibrate according to the needle spatial errors withregards to the punctured target.

Different actuators are commercially available with particular technicalspecifications, mainly in terms of vibration intensity and size.Miniature loudspeakers, electromagnetic alarm buzzers and coin motorsare routinely used.

When compared to other solutions, coin motors offers low cost, smallsize, low voltage and reduced noise devices, being used in routinelydevices, e.g., mobile phones. Therefore, coin vibration actuators308-100 Pico Vibe were used to deliver this kind of feedback. Table 4show important actuator manufacturer specifications.

TABLE 4 308-100 Pico Vibe operation characteristics. CharacteristicValue Diameter 8 mm Height 3.4 mm Typical Normalized Amplitude 0.7 GRated Operating Voltage 3V DC Rated Vibration Speed 12000 OperatingCurrent 70 mA Vibration efficiency 3.2 g/W Noise output 50 dB TypicalLag Time 51 ms Typical Rise Time 77 ms Typical Stop Time 65 ms

Based on a literature research [14], 8 motors were chosen and placed atthe 8 cardinal points (equally placed around the head).

Four control strategies were implemented and tested. Each strategy issimilar to the ones already described for the 3D sound interface (SS1,SS2, SS3 and SS4), but now a coin motor will vibrate instead of playinga sound source.

The sound loudness, Ssleep and distance to the target are nowtransmitted from the KidneyNav to the Arduino Uno platform wirelesslyvia a Bluetooth® connection. The Arduino, based on the Atmega328Pmicrocontroller, is responsible for interpreting and processing thereceived information and activating/deactivating the respectiveactuators.

The sound loudness (values from 0 to 1) is used to control the vibrationintensity Vi, as a percentage of the maximum possible vibration. Thevibration sensation is achieved by individually controlling the supplyvoltage using a square wave signal generated by pulse width modulation(PWM).

Each motor was further connected to a 3.3 V pin at the Arduino. A diodewas reversely connected to the motor to protect the microcontrolleragainst voltage spikes. 8 transistors 2N2222 were used to assurehigh/low current outputs, to activate/deactivate each motor.

The following pertains to experiments. Different experiments wereperformed in order to evaluate the accuracy and acuity of each interfacein an individual or combined way.

The following pertains to sound parameter settings. The soundparameters, such as frequency and duration were found empirically byindividually playing and adjusting each source parameters with manualcontrol. To this extent 16 participants listened sounds that werecreated with sinusoids which frequency vary from 300 Hz to 1200 Hz. Inthe end, they indicate the frequency that they were most comfortablewith. Based on such results, one found that the preferred values for thefirst and second sound strategies (SS1 and SS2) were:

Sf=700 Hz;

Sp=0;

Sd=50 ms;

S₂f=950 Hz or 400 Hz;

maxSleep=800 ms;

minSleep=50 ms;

max_(dist)=150;

min_(dist)=0;

When evaluating the SS3 strategy, one found that front and back soundscan be well discriminated when Sf_(front)=690 Hz while Sf_(back)=490 Hz.

Finally, a sinusoidal sound, with S₄f=1200 Hz and S₄d=25 ms, wasintroduced when testing the SS4. Moreover, the frequency of the sourceswith positions at the most left, right, up and down were changed to 650Hz, 650 Hz, 730 Hz and 460 Hz, respectively. The other sources remainedthe same Sf_(front) and Sf_(back) frequencies.

One found that the target can be reached accurately when T_(err)=2 mm.SS2 was discarded for testing because all users prefer the SS1 approach.

It should be highlighted that the user can manually control theheadphones volume.

The following pertains to localization accuracy test. A set oflocalization experiments were firstly performed to determine whether aperson is able to perceive the direction of random sources or vibrationstimulus.

An audio stimuli was presented to the listener with Razer Tiamat 7.1headphones. This headphones have 10 discrete drivers (5 for each ear)composed by neodymium magnets with 30 mm of diameter and a frequencyresponse between 20 Hz and 20.000 Hz. They were connected to a PC via a7.1 Surround Sound-enabled Sound Card.

On the other hand, the developed headband was used to create avibrotactile feedback.

Before any experiment, a brief demonstration was given to eachparticipant and they were allowed to test any sensorial feedback up to 2minutes, so that they become comfortable and familiarized with thesystem.

During either audio or vibration experiments, each time the user wasready, a sound or a vibration actuator was activated randomly from a setof possible locations at the same distance from the listener.

The chosen strategy for starting the experiment was also determinedrandomly.

Each sound strategy (SS1, SS3 and SS4) was tested for all the threespatial configurations. In contrast, the vibrotactile feedback wastested in a single distribution. Each exercise was repeated 16 times.

The users had up to 2 seconds to report the location of the perceivedsound or vibration, by marking the perceived location in a printedsheet.

In total 31 volunteers participated: 26 medical students and 5 surgeondoctors. During experiments, they had no feedback about the correctnessof their answers.

The aim of this test was to select the best audio spatial configuration,sound strategy and finally compare audio against vibration as possiblefeedback systems.

The following pertains to phantom test. Despite of the accuracy ofdetecting single vibration or audio sources it is important to test theefficiency of all interfaces for needle guidance. To this extent, aphantom study was performed to test and evaluate the most valuablefeedback interface. The following configurations were tested in aphantom box:

3D view

NeedleView

Audio

Vibration

3D view+NeedleView

Audio+NeedleView+3D view

Vibration+NeedleView+3D view

The phantom box was made of wood without any ferromagnetic material toavoid interferences that might reduce the precision of the trackingdevice. A sponge material with 8 cm of thickness was used to simulatethe skin, offering some resistance, low deformability and opaque texturewhen inserting the needle.

A small plastic arm was attached to one side of the phantom with a 10-15cm distance from the superficial sponge material. It was used to holdthe catheter sensor at different locations inside the phantom box.

When using only vibration or audio, the participants were blindedthroughout all planning and puncture procedure. An audio message “targetachieved” and a vibration pattern (all motors vibrate at the same time)were used to aware the participants when they reach the target (puncturesuccess).

Puncture success was accomplished when the root mean square distance wasless than 3 mm. The planning and puncture time were recorded. Needleposition was then verified using a webcam showing the phantom interior.The degree of the needle tip divergence was calculated, during wholeinsertion procedure, by storing the root mean square distance betweenthe real and virtual path.

The main objective was to assess whether the guidance approach increasesthe procedure efficiency, in terms of the duration, mean velocity, meanand maximum error.

The testing order was randomized to reduce target position-relatedfamiliarization and learning issues. Otherwise, the last guidance aspectwill had an advantage over the first technique due to experienceperforming the puncture.

Different medical professionals with diverse expert degrees performedthree times each strategy. These tests were performed by 2 differentgroups: naive (n=56 without any or less than 2 years of medicalexperience) and expert (n=15 with more than 2 years performing minimallyinvasive surgeries). At the beginning of each experiment the participantwas allowed to practice by reorientation the needle in the air and byperforming up to 2 puncture attempts. This data is not included for thestatistical analysis.

At the end of each test, the participant filled a questionnaire to scoreeach approach according to the following questions:

-   -   Q0: Score each approach from 1 (most favorite) to 10 (least        favorite);    -   Q1: Each approach based on the time needed to look to the screen        from 1 (mandatory visualization throughout all procedure) and 10        (no need for visualization);    -   Q2: The difficulty of the procedure from 1 (very difficult) to        10 (straightforward);    -   Q3: The effort to familiarize with the technique from 1 (very        difficult) to 10 (straightforward);

The following pertains to animal trials. The animal trials wereperformed as already described. In particular, the following pertains toresults, further in particular of a localization accuracy test. Thetotal duration of each experiment was about 10 minutes. FIG. 9 shows thepercentage of times that the target location was correctly chosen forwhole participants. FIG. 10 shows the average and standard deviationerrors between the marked source and target one.

When comparing the different sound strategies and audio spatial worlds,best results were achieved when using 12 audio sources together with SS4strategy (SS4-12SC, FIG. 6-c). Within this configuration, target sourceswere correctly chosen 79.2±8.1% of times with an average angulationerror of 10.4° degrees. The worst configuration was found with SS1strategy when using 16 audio sources (SS1-16SC—FIG. 6-b), showing anaverage angulation error of 51.5° degrees and an assertive percentage of43±6.0%.

SS4 was the best sound strategy with significant statistical differences(two-way ANOVA—see attachment 1 for more detail) when compared to SS1(p<0.0001) and SS3 (p<0.05). SS4 was followed by SS3 that also showssignificant statistical differences with SS1 (p<0.01). Finally, worstresults were obtained with SS1. Regarding the audio world configuration,12SC was the best one with significant statistical differences whencompared to 8SC (p<0.0001) and 16SC (p<0.0001). It was followed by 8SCwith also significant statistical differences with 16SC (p<0.0001).Finally, worst results were obtained with SS1.

When listening the various sources configured with SS1, the user caneasily separate left from right. However, only 62% of times he was ableto identify if the sound is created at the front or back sources,creating high standard deviations between users (FIG. 10).

From the boxplot analysis (FIG. 10), more than 75% of participants didnot show angulation errors when using the SS4-8SC and the vibrationfeedback.

By introducing Sf_(front) and Sf_(back) in SS3 and SS4 strategies, theuser was able to improve its ability of detecting front or back sound to87% of times.

By adding S₄f and S_(f)d to SS4, the user was able to accurately andpromptly distinguish the sources placed at the four cardinal points (0°,90°, 180° and 270°) when compared to SS1 or SS3 (71% vs. 90.5%).

Finally, vibration results were the best ones. The participants caneasily and accurately identify vibration sources 91.1±3.6% of times withan average angulation error of 8.0° degrees. Significant statisticaldifferences (p<0.0001) were found when compared to the best audioconfiguration (SS4-12SC).

The following pertains to phantom test. In terms of the phantom test,every subject reached the correct target in their first attempt. FIG. 11shows the average time for planning and puncturing in both naive andexpert groups. Clearly, NeedleView alone or combined with any othermodalities was the fastest strategy for planning or puncturing.

On the other hand, audio or vibration alone were the ones that tooklonger times.

Planning significant differences between naive and expert groups wereonly found when using audio feedback (p<0.01). Puncture significantdifferences between both groups were found when inserting the needleunder 3D view (p<0.05). 3D, audio and vibration are the methodologieswhere participants show quite range of times, especially for planning.In the naive group, planning time was minor when using the NeedleViewalone (average value of 4.5±1.5 s). Higher times were achieved using theAudio feedback (21.3±15.1 s). In terms of the puncture step, bestresults were achieved using “3D view+NeedleView+Vibration” with anaverage value of 14.7±8.5 s. Surprisingly, longer puncture results wereachieved with the 3D view with an average time of 34.8±21.0 s.

FIG. 12 shows multiple comparisons between all guidance strategies.Statistical analysis show that all new interfaces influenced positivelythe procedure performance when comparing to only the 3D views presentedpreviously.

In the expert group, planning time was minor when using “3Dview+NeedleView+Audio” with an average value of 2.7±0.6 s.

Higher times were achieved using the Vibration (16.8±8.1 s). Withrespect for the puncture step, best results were achieved when using “3Dview+NeedleView+Audio” with an average value of 15.2±7.7 s. Longer timeswere needed when using the Audio feedback with an average value of29.1±8.0 s.

The time needed for planning and puncturing is very promising, existingno statistical differences when comparing experts to naive participantsin most of guidance strategies.

FIG. 13 and FIG. 14 give an overview about common puncture profiles wheninserting the needle with different feedbacks. As represented, usingonly the 3D view it was difficult to maintain the needle tip inside the2 mm margin (white circle at the NeedleView). Errors were minimal whenusing “3D view+NeedleView”+“Audio” or “Vibration”, because an audio orvibrotactile alert was generated each time the user increases thiserror. Similar errors during puncture were found when using the audio orvibration standalone, but with higher planning and puncture times.

Audio and vibration feedback seemed to precisely inform the user to keepthe needle correctly aligned with the target.

All participants considered that audio or vibration feedback gives lessconfidence than the NeedleView, but suggested that can improve the PRAprocedure. Although impractical in a real situation, results reveal thatthe target can be reached without spending any time looking on thescreen.

The step function to control the audio loudness was easy to understandfor whole users. Although one tested also an exponential function(Equation 5), this option was never preferred.

loudness=0.0326e″ ^(0.0799·err)  Equation 5

The audio feedback combined with the NeedleView provided gooddirectional feedback during all the procedures. This interface was thepreferred and simplest one without needing any training before usage. Inthe presence of the NeedleView, the 3D view was frequently ignored andthe audio or vibrotactile were mainly used as a warning system than aguiding one.

Table 5 shows the questionnaire for questions Q0, Q1, Q2 and Q3 (seeexperiments above).

TABLE 5 Questionnaire results when evaluating the different guidanceapproaches. 3D + 3D + 3D + NeedleView + NeedleView + Questions 3DNeedleView Audio Vibration NeedleView Audio Vibration Q0 6.25 ± 0.96 9.2± 0.7 5.3 ± 1.2 5.9 ± 1.1 8.8 ± 1.6 8.7 ± 0.7 6.3 ± 2.1 Q1 1 1 10 10 15.4 ± 1.2 5.2 ± 1.5 Q2 3.8 ± 2.3 10 2.9 ± 1.1 5.5 ± 0.7 9.5 ± 0.5 9.6 ±0.5 9.5 ± 0.5 Q3 4.3 ± 1.9 10 2.5 ± 0.5 5.7 ± 1.4 9.1 ± 1.1 8.9 ± 1.28.7 ± 1.5

The NeedleView followed by the “3D+NeedleView” and “3D+NeedleView+Audio”were the three most favorite methods according to Q0.

Whole users score Audio and Vibration in Q1 with 10, because they wereblindfolded when performing the procedure. In contrast, visualmodalities were scored with 1. Hybrid modalities that combines Visualand Audio/Vibration feedback were scored with similar values.

Regarding the question Q2, audio feedback, followed by the 3D screen,were the most difficult techniques. The easier ones were the NeedleViewalone or combined with any other feedback.

Finally, Audio feedback was the most difficult technique with thehighest learning curves. The NeedleView was the easiest andstraightforward one, with no need for training.

The following pertains to animal trials. Eight surgeons haveparticipated in this experiment. In order to not sacrifice many animals,surgeons start this experiment by choosing three guidance approaches.“NeedleView+3D view”, “Audio alone” and “NeedleView+3D view+Audio” werethe selected ones. A surgical setup is represented in FIG. 15.

Three pigs were used for this experiment. Six successful tracts to themiddle of ureter were accomplished. Each ureter was punctured up to 4times in different regions.

Due to animal's small anatomy, it was only possible to place theureterenoscope into a kidney calyx in two pigs. Therefore, statisticalanalysis was only performed for the ureter experiments.

Results are in accordance with results already presented. 100% successrates were reached with only one attempt for almost all cases.

The time needed to see the needle tip in the ureter skin (FIG. 16-a to-d) was some seconds, but the time needle to perforate the ureter skin(FIG. 16-e) was more than 1 minute. The problem is that the ureterslipped and moved away when the needle was trying to perforate.

FIG. 17 presents the average times for planning and puncturing until theneedle tip is visualized in the ureterenoscope camera.

Results are in accordance with the ones described with the phantom test.Longer times were obtained when performing the experiment with audioalone. Statistically significant differences were found when comparingthe audio with any of the other two interfaces for surgical planning(p<0.0001) and puncturing (p<0.001).

No significant differences were found when comparing the “NeedleView+3Dview” and “NeedleView+3D view+Audio”. But as already described in thephantom test, that audio feedback helped the surgeon keeping the correctpath with minor deviations (FIG. 14).

No major problems were found during the experiments and the mosttime-consuming. One attempt was needed for all surgeons.

The following pertains to further discussion. Although the KidneyNavframework already allowed surgeons to comprehend the volumetric data ofthe collecting system and to follow a 3D path, now one explores thepossibility of adding additional feedback, by recurring to the hearingand touch senses.

It was tested multiple interfaces where audio and vibrotactile senseswere combined with visual information to provide and improve insightinto complex PRA trajectories. These new ways of feedback intended notto replace visual guidance, but complement the surgeon interaction withthe needle, being able to anticipate any movement even without lookingto a monitor.

With this multi-sensorial interface, the surgeon must place the needleat the skin surface, align with respect to the target, and finally heshould puncture the kidney according to this approved angle. When theneedle is being inserted from an incorrect angle, it will miss theanatomic target which error is dependent on the angulation error. Thiserror (originated at possible needle deflection, soft tissuedisplacements and human tremors) can be tracked in real-time using the3D EMT sensors at the needle and catheter tips and used to generate aset of visual, audio or vibration signals.

The previously framework, based in a 3D view, requires some learningtraining. Results show that by using this view, is was not possible toprecisely and easily follow a pre-computed trajectory with minimaldeviations from the correct path. Regardless the user experience, he caneasily misunderstood the 3D information, increasing the probability ofhigh errors.

By using the NeedleView, the user was able to automatically andintuitively classify the error as safe and dangerous. No training wasrequired within this interface, being a ready-to-use approach.Experimental results show that NeedleView worked reasonably well for allpuncture orientations being the fastest and preferred guidance aspect.

The headphones produces different spatialized sound signals relating theposition of the needle with the target. Different sound frequencies weretested to create accepted tones for all users. If the needle iscorrected aligned no sound was generated, avoiding possible annoyanceand distractions.

Other works have reported different angulation errors around the headusing headphones: 22.3°, 26°, 34.2° [13] and 22.2°. When compared tothese works, results show reduced angulation errors when using the SS4sound strategy with 12 source sounds (75% of participants show errorsbelow 20°). The poorest scenario was shown at SS1-16SC due to theinability to clearly distinguish from front and back sounds, as wellsources separated from small angles.

Although it provided limited spatial information, 3D audio feedback wasenough to accurately guide the surgeons without never looking to thescreen (in phantom test and animal trial). By using different audiointensities and pitches, it was possible to improve the feedback aboutthe amount and direction of the actual deviation from the preferredtrajectory.

As already reported, error angles are higher for headphones than forloudspeakers. Although surrounding loudspeakers will have better soundspatial accuracy, is unpractical to implement inside an operating room,due to all the medical armamentarium. Moreover, since the listener headmust be centered with the sound system, 7.1 headphones presented apreferred solution to deal with these problems.

When studying the effect of vibration for guidance, results show thatthe source motors can be correctly identified with percentages higherthan 90% for an 8-site configuration. Our results are in accordance witha recently described work [14], that tests the efficacy of providingvibration feedback using a headband holding 12 coin-type motors.

Although vibration was easily to understand and learn than audio, oftenusers prefer the audio feedback combined with the NeedleView plus Audio(Table 5).

When using only audio or vibration feedback alone, the average timeneeded for planning or puncturing was significantly superior whencompared to the NeedlleView. But when combined, this feedback helped tofollow the pre-planned trajectory with minor deviations (FIG. 14). Ifcorrectly used, the disclosure exhibited potential to decrease cognitiveload and alert the surgeon when the needle is moving away from theaccurate path without the need to continuously interpret analyze anyguidance monitor. Now, the surgeon may devote more attention to theactual needle insertion and patient conditions.

The term “comprising” whenever used in this document is intended toindicate the presence of stated features, integers, steps, components,but not to preclude the presence or addition of one or more otherfeatures, integers, steps, components or groups thereof.

Flow diagrams of particular embodiments of the presently disclosedmethods are depicted in figures. The flow diagrams illustrate thefunctional information one of ordinary skill in the art requires toperform said methods required in accordance with the present disclosure.

It will be appreciated by those of ordinary skill in the art that unlessotherwise indicated herein, the particular sequence of steps describedis illustrative only and can be varied without departing from thedisclosure. Thus, unless otherwise stated the steps described are sounordered meaning that, when possible, the steps can be performed in anyconvenient or desirable order.

It is to be appreciated that certain embodiments of the disclosure asdescribed herein may be incorporated as code (e.g., a software algorithmor program) residing in firmware and/or on computer useable mediumhaving control logic for enabling execution on a computer system havinga computer processor, such as any of the servers described herein. Sucha computer system typically includes memory storage configured toprovide output from execution of the code which configures a processorin accordance with the execution. The code can be arranged as firmwareor software, and can be organized as a set of modules, including thevarious modules and algorithms described herein, such as discrete codemodules, function calls, procedure calls or objects in anobject-oriented programming environment. If implemented using modules,the code can comprise a single module or a plurality of modules thatoperate in cooperation with one another to configure the machine inwhich it is executed to perform the associated functions, as describedherein.

The disclosure should not be seen in any way restricted to theembodiments described and a person with ordinary skill in the art willforesee many possibilities to modifications thereof. The above describedembodiments are combinable. The following claims further set outparticular embodiments of the disclosure.

What is claimed is:
 1. A guidance system configured to dynamically guidea surgical needle catheter onto an organ of a patient comprising: anelectromagnetic catheter configured to be inserted into the patient andfor defining a desired location to be reached by the surgical needlecatheter; an electromagnetic tracker configured to track of a locationand orientation of the surgical needle catheter; and an electronic dataprocessor arranged for: displaying a 2D concentric-ring target;continuously displaying a projection of a line concurrent or coincidentwith the surgical needle catheter onto said target, wherein said targetis on a plane intersecting a tip of the electromagnetic catheter and theplane being perpendicular to the orientation of the surgical needlecatheter; and continuously displaying a plurality of concentric ringscentred around the tip of the electromagnetic catheter.
 2. The guidancesystem according to claim 1, wherein said concentric rings comprise aninner ring corresponding to a predetermined surgically acceptable regionfor the surgical needle catheter.
 3. The guidance system according toclaim 1, wherein said inner ring is centred around the tip of theelectromagnetic catheter and has a radius of less than or equal to 1 mm,of less than or equal to 2 mm, of less than or equal to 3 mm, of lessthan or equal to 5 mm, of less than or equal to 8 mm, or of less than orequal to 10 mm.
 4. The guidance system according to claim 1, whereinsaid concentric rings comprise an intermediate ring corresponding to apredetermined surgically inacceptable region for the surgical needlecatheter.
 5. The guidance system according to claim 1, wherein saidintermediate ring is centred around the tip of the EM catheter and has aradius of less than or equal to 25 mm, of less than or equal to 30 mm,of less than or equal to 35 mm, of less than or equal to 40 mm, of lessthan or equal to 45 mm, or of less than or equal to 50 mm.
 6. Theguidance system according to claim 1, wherein said concentric ringscomprise a further ring having a variable diameter depending on aspatial difference between surgical needle catheter tip and the target.7. The guidance system according to claim 6, wherein said further ringhas a visual characteristic which is changed when the surgical needlecatheter tip deviates from the target, wherein the visual characteristicis changed when the surgical needle catheter tip goes beyond the target.8. The guidance system according to claim 7, wherein said visualcharacteristic is a colour of the further ring, a thickness of thefurther ring, a fill-in of the further ring, or combinations thereof. 9.The guidance system according to claim 1, comprising a 3D soundinterface configured to provide spatialized sounds according to aspatial difference between the surgical needle catheter tip and thetarget.
 10. The guidance system according to claim 1, comprising avibration interface configured to provide spatialized vibration feedbackusing vibration motors, according to the spatial difference between thesurgical needle catheter tip and the target.
 11. The guidance systemaccording to claim 1, wherein the plurality of concentric rings aredisplayed around the target on the plane intersecting a tip of theelectromagnetic catheter and being perpendicular to the orientation ofthe surgical needle catheter.
 12. The guidance system according to claim1, comprising the surgical needle catheter arranged for surgicaloperation of the organ.
 13. The guidance system according to claim 12,wherein said organ is the kidney and the dynamically guiding of thesurgical needle catheter is for percutaneous renal access.
 14. Theguidance system according to claim 1, wherein the ring target isdisplayed on one or more displays.
 15. The guidance system according toclaim 1, wherein the ring target is displayed in a virtual reality oraugmented reality display.
 16. A method for operating a guidance systemfor dynamically guiding a surgical needle catheter onto an organ of apatient, said system comprising an electromagnetic catheter configuredfor insertion into the patient and for defining a desired location to bereached by the surgical needle catheter; an electromagnetic trackerconfigured to track a location and orientation of the surgical needlecatheter; and an electronic data processor; said method comprisingcarrying out by said electronic data processor the steps of: displayinga 2D concentric-ring target; continuously displaying a projection of aline concurrent or coincident with the surgical needle catheter ontosaid target, wherein said target is on a plane intersecting a tip of theEM catheter and the plane being perpendicular to the orientation of thesurgical needle catheter; and continuously displaying a plurality ofconcentric rings centred around the tip of the electromagnetic catheter.17. The method according to claim 16, wherein said concentric ringscomprise an inner ring corresponding to a predetermined surgicallyacceptable region for the surgical needle catheter, wherein said innerring is centred around the tip of the electromagnetic catheter andhaving a radius of less than or equal to 1 mm, of less than or equal to2 mm, of less than or equal to 3 mm, of less than or equal to 5 mm, ofless than or equal to 8 mm, or of less than or equal to 10 mm.
 18. Themethod according to claim 16, wherein said concentric rings comprise anintermediate ring corresponding to a predetermined surgicallyinacceptable region for the surgical needle catheter, wherein saidintermediate ring is centred around the tip of the electromagneticcatheter and having a radius of less than or equal to 25 mm, of lessthan or equal to 30 mm, of less than or equal to 35 mm, of less than orequal to 40 mm, of less than or equal to 45 mm, or of less than or equalto 50 mm.
 19. The method according to claim 16, wherein said concentricrings comprise a further ring having a variable diameter depending on aspatial difference between surgical needle catheter tip and the target.20. The method according to claim 19, wherein said further ring has avisual characteristic which is changed when the surgical needle cathetertip deviates from the target, wherein the visual characteristic ischanged when the surgical needle catheter tip goes beyond the target.21. The method according to according claim 20, wherein said visualcharacteristic is the colour of the further ring, the thickness of thefurther ring, the fill-in of the further ring, or combinations thereof.22. The method according to claim 16, further comprising using a 3Dsound interface that provides spatialized sounds according to thespatial difference between surgical needle catheter tip and target. 23.The method according to claim 16, further comprising using a vibrationinterface that provides spatialized vibration feedback using vibrationmotors, according to the spatial difference between surgical needlecatheter tip and target.
 24. The method according to claim 16, whereinsaid organ is the kidney and the dynamically guiding of the surgicalneedle catheter is for percutaneous renal access.
 25. A non-transitorycomputer-readable information storage media having stored thereoninstructions that when executed by a processor perform a method in aguidance system for dynamically guiding a surgical needle catheter ontoan organ of a patient, said system comprising an electromagneticcatheter configured for insertion into the patient and for defining adesired location to be reached by the surgical needle catheter; anelectromagnetic tracker configured to track a location and orientationof the surgical needle catheter; and an electronic data processor; saidmethod comprising: displaying a 2D concentric-ring target; continuouslydisplaying a projection of a line concurrent or coincident with thesurgical needle catheter onto said target, wherein said target is on aplane intersecting a tip of the EM catheter and the plane beingperpendicular to the orientation of the surgical needle catheter; andcontinuously displaying a plurality of concentric rings centred aroundthe tip of the electromagnetic catheter.
 26. A guidance systemcomprising: an electromagnetic device configured to be inserted into abody and defining a desired target to be reached by an operative device;an electromagnetic tracker configured to track a location andorientation of the operative device; and a processor and memoryconfigured to: displaying a 2D concentric-ring target on a displaydevice; continuously display a projection of a line concurrent orcoincident with the operative device onto a target, wherein the targetis on a plane intersecting a tip of the electromagnetic device, and theplane is perpendicular to an orientation of the surgical device; andcontinuously updating the display of a plurality of concentric ringscentered around the tip of the electromagnetic device.
 27. The guidancesystem of claim 26, further comprising a vibrotactile headbandconfigured to provide tactile feedback which supplements the displayedinformation.
 28. The guidance system of claim 26, further comprising 7.1headphones configured to provide audio feedback which supplements thedisplayed information.
 29. The guidance system of claim 26, wherein oneor more of the concentric rings have a visual characteristic which isupdated when the operative device deviates from the target, wherein thevisual characteristic is changed when the operative device goes beyondthe target.
 30. The guidance system of claim 29, wherein the visualcharacteristic is a color of one or more of the rings, a thickness ofone or more of the rings, and/or a fill-in of one or more of the rings.